Cerebrospinal Fluid GABA Research Articles

Cerebrospinal fluid GABA measurements: basic and clinical considerations.

The valid measurement of GABA concentration in the CSF for studying in vivo alterations of central nervous system GABAergic activity requires that consideration be given to several factors that affect GABA concentration. These factors include in vivo variables such as the caudocranial concentration gradient in CSF, age, sex, precursor intake, medications, and physical activity, as well as in vitro alterations that can occur during collection, storage, preparation of sample, and analysis. The influence of these factors can be minimized with proper methodology.

Gamma-Aminobutyric acid concentrations in the cerebrospinal fluid of newborn infants.

gamma-Aminobutyric acid (GABA) concentrations in cerebrospinal fluid (CSF) were measured in 20 neonates with various gestational and postnatal ages. These concentrations varied between 9 and 45 nmol/ml which is approximately 20-100 times the concentrations found in adults. CSF GABA concentrations tended to decrease with advancing gestational age. No apparent alterations were noted with increasing postnatal age (until 6 weeks of age). Asphyxia but not neonatal sepsis was accompanied by an increase in CSF GABA concentrations compared to respective controls.

Transport of GABA at the Blood‐CSF Interface

The entry of GABA into cerebrospinal fluid (CSF) was studied in dogs anesthetized with pentobarbital and relaxed with suxamethonium. GABA was administered intravenously as a priming dose and subsequent maintenance infusion to compensate for the rapid elimination of the amino acid. Steady state concentrations of GABA in CSF were reached between 10 and 60 min after injection, the rate of entry tending to decrease with increasing plasma levels. During steady state conditions CSF concentrations showed great interindividual differences and varied between 0.03 and 5.1% of those in plasma. Probenecid and sodium valproate considerably enhanced the CSF/plasma concentration ratio of GABA. When GABA was directly injected into the liquor space, probenecid slowed down the elimination of GABA from CSF. The results suggest a transport of GABA into and out of CSF, the outward transport being inhibited by probenecid and sodium valproate.

Cerebrospinal fluid GABA levels in various neurological and psychiatric diseases.

Cerebrospinal fluid gamma-aminobutyric acid (CSF-GABA) was analysed by radioreceptor assay in 16 normal controls and 84 patients with various neurological and psychiatric diseases. In patients with spinocerebellar degeneration, neuro-Behçet's syndrome and Parkinson's disease, CSF-GABA levels were decreased. On the other hand, increased CSF-GABA levels were detected in patients with meningitis.

Alterations of central GABAergic activity in neurologic and psychiatric disorders: evaluation through measurements of GABA and GAD activity in cerebrospinal fluid.

Glutamic acid decarboxylase (GAD) is generally thought to be the primary catalyst mediating the formation of γ-aminobutyric acid (GABA), which in turn is thought to be the main inhibitory neurotransmitter in the central nervous system (CNS) (1). For this reason GAD activity in CNS tissue has been widely investigated because of the possibilities that it may serve a role in the regulation of central GABAergic activity or that it may provide a reflection of CNS GABAergic alterations associated with certain neurologic or psychiatric disorders. Efforts to elucidate the involvement of GAD alterations in the pathology of CNS disorders have benefitted from studies of animal models and human autopsy tissue (e.g., 2–8). However, in many instances it has not been possible to develop entirely suitable animal models. The diseased human would be the only perfect model for these disorders except, of course, human brain tissue can seldom be studied except at autopsy. Thus, especially in clinical studies, variables are difficult to control and great care must be exercised in extrapolating data to the living human condition.

Cerebrospinal fluid GABA and cyclic nucleotides in alcoholics with and without seizures.

Cerebrospinal fluid levels of gamma-aminobutyric acid (GABA) and cyclic nucleotides were measured in alcoholic and control patients. Alcoholics without seizures had higher GABA levels than either alcoholics with seizures or controls. Levels of cyclic AMP and cyclic GMP in cerebrospinal fluid of controls and alcoholics with and without seizures were not significantly different.

Effect of isoniazid on cerebrospinal fluid and plasma GABA levels in Huntington's disease

During a double-blind placebo controlled trial, γ-aminobutyric acid (GABA) was measured in cerebrospinal fluid (CSF) and plasma obtained from patients with Huntington's Disease prior to the start of the trial, at the end of the placebo period and following treatment with isoniazid. The results showed that the GABA concentrations in CSF tripled following treatment with isoniazid although no significant change occurred in plasma GABA levels. This finding in humans indirectly confirms reports of a similar increase of brain GABA content in experimental animals following isoniazid treatment and provides additional evidence that CSF GABA measurements reflect brain GABA activity.

GABA and homocarnosine in CSF: The relationship to brain GABA content

GABA concentrations in cerebrospinal fluid (CSF) and brain of rats were determined before and after intraperitoneal injection of drugs that increase brain GABA levels. In untreated rats there is very little free GABA in the CSF (65 ± 12 pmol/ ml) but considerable amounts of conjugated GABA (2885 ± 100 pmol/ ml). Homocarnosine was identified as the major GABA conjugate (2110 ± 110 pmol/ ml). After administration of γ- vinyl GABA CSF concentrations of free GABA, total conjugated GABA and homocarnosine rise in a dose-dependent manner. There is an exponential correlation between whole brain GABA and free CSF GABA concentration. Brain GABA levels are linearly correlated with CSF concentrations of total conjugated GABA and homocarnosine. Ethanolamine-0-sulfate, at a dose not affecting brain GABA concentrations, markedly increases serum GABA but only minimally affects CSF GABA levels. This suggests that concentrations of GABA in the CSF are primarily related to brain GABA levels. Determination of CSF concentrations of free or conjugated GABA may be useful for the estimation of brain GABA levels in patients on therapy intended to alter brain GABA concentrations.

Selection of control populations for clinical cerebrospinal fluid GABA investigations based on comparison with normal volunteers

Altered cerebrospinal fluid (CSF) GABA levels have been implicated in various neurologic and psychiatric disorders, therefore, the establishment of the normal range of human CSF GABA is essential. The GABA content in 111 samples of lumbar CSF from 87 drug-free normal individuals obtained from three medical centers was measured by ion-exhange/fluorometric assay. The overall mean value (± SD) was 214 ± 74 pmol/ ml; however, significant variations in lumbar CSF GABA concentrations with respect to age, sex, and aliquot were documented among homogeneous subgroups of the overall population. CSF GABA levels were negatively correlated with age among females ( p<0.01). The data illustrate the importance of obtaining fraction-matched CSF specimens from age-and sex-matched normal individuals to serve as the reference group for statistical comparisons in clinical CSF GABA investigation.

Schizophrenia: Low spinal fluid GABA levels?

Cerebrospinal fluid (CSF) GABA levels were determined in the spinal fluid of 17 drug-free schizophrenic patients and of 40 normal volunteers. Following lumbar puncture in fasting patients maintained at bed rest, CSF from the 16th to the 20th cc was collected, placed on ice immediately and frozen at −70°C within one hour. CSF GABA was measured by a modified cation exchange chromatography. Schizophrenic patients showed significantly lower CSF GABA levels (191 ± 9 pmol/ ml) compared to normal controls (233 ± 13 pmol/ ml; p<0.01). CSF GABA levels were significantly correlated with duration of illness ( r=0.54) and number of hospitalizations ( r=0.50), but not with severity of psychosis or age of onset. A negative correlation with CSF glucose levels was observed ( r=−0.61). These data suggest that if a GABA deficit is present it only will be observed early in the illness and may disappear with chronicity.

Effects of dopaminergic drugs on cerebrospinal fluid GABA concentration in Parkinson's disease

Increased striatonigral GABAergic activity reduces striatal dopamine turnover. We measured cerebrospinal fluid (CSF) GABA concentrations in untreated and treated parkinsonian patients and control subjects. The 4 ml sample of cerebrospinal fluid for GABA assay (radioreceptor method of Enna et al.) was collected after 20 ml of CSF had been removed. It was immediately frozen and assayed within six weeks. The mean concentration ( ± SEM) of CSF GABA in untreated parkinsonian patients and control subjects was 181 ( ±34) and 203 ( ± 5) pmoles/ml, respectively. In treated parkinsonian patients taking either levodopa/carbidopa (mean daily dose ± SEM, 1150 115 ± 240 24 mg ) or lergotrile (mean daily dose 50 mg), the mean CSF GABA concentrations ( ± SEM) were 184 ( ± 31) and 215 ( ± 22) pmoles/ml, respectively. Our results suggest that the concentration of released GABA is normal in Parkinson's disease and dopaminergic drugs do not modify the activity of GABAergic neurones.

Sites of origin and rostrocaudal concentration gradients of GABA in cerebrospinal fluid

GABA in Cerebrospinal fluid (CSF) appears to have a central origin because contamination of CSF with GABA from peripheral sources does not appreciably occur with intact blood-brain/CSF barriers. Further refinement of its contributing sources in lumbar CSF is crucial for clinical interpretations. Sequential lumbar CSF aliquots were obtained from neurologic patients. CSF samples assayed by the radioreceptor method had 202 ± 23, 243 ± 37 and 298 ± 35 pmol GABA/ml (SE) in the 8th, 24th and 40th ml fractions, respectively. The mean GABA concentrations in the 8th and 40th ml of CSF were significantly different ( p<0.05). Similarly, the GABA content in CSF samples assayed by the ion-exchange/fluorometric method had a mean 2% increase per additional ml collected after the initial aliquot. Since low lumbar CSF GABA levels have been demonstrated in neurologic disorders associated with deficiences in brain GABA, lumbar CSF GABA appears to reflect brain GABA content. However, bulbar/spinal degenerative disorders may also lower lumbar CSF GABA content.

Cerebrospinal fluid GABA in normals and patients with affective disorders

Cerebrospinal fluid GABA was measured in 41 normal volunteers, 16 depressed and eight manic patients during a medication-free evaluation. CSF GABA was measured by modified cation-exchange chromatography. Mean CSF GABA in the normal volunteers was 231.8 ± 12.5 pmole/ ml, nonsignificantly different from that in the depressed patients (209.1 ± 13.8) or manics (211.4 ± 21.7). In one rapidly cylcing patient values during his manic episodes were significantly higher than those during depressed periods ( p<0.05). In the normals CSF GABA was positively correlated ( p<0.05) with CSF norepinephrine and MHPG and negatively correlated with CSF calcium and magnesium. In the depressed patients and in normal females, but not males, GABA was negatively correlated with age. There was no significant correlation between CSF GABA and degree or severity of rated depression, anxiety, or psychosis. Affectively ill patients treated with the anticonvulsant carbamazepine did not demonstrate significant alterations in CSF GABA concentrations.

Factors influencing concentrations of GABA in cerebrospinal fluid

Degradation of cerebrospinal fluid (CSF) constituents occurring during collection, storage and analysis may add artifactual variations to CSF data. GABA levels in untreated CSF determined by ion-exchange/fluorometric assay remained stable when stored at −70°C for 3.5 years and at −20°C for 1.5 years. GABA concentrations in untreated CSF doubled during 2 hours at room temperature but did not significantly change during 10 minutes at room temperature or 2 hours at 4°C. GABA levels in deproteinized CSF were stable at −70°C but doubled during 11 months of storage at −20°C. GABA concentrations in deproteinized CSF were stable for 49 hours at room temperature but increased 1.3 -fold and 2.0 -fold after 3 weeks at 4°C and room temperature, respectively. The GABA content of homocarnosine standards in 0.1 N HCl similarly increased during storage at room temperature and at −20°C suggesting that the GABA elevations in inadequately stored or prepared CSF may be secondary to GABA-containing peptide degradation.

Cerebrospinal fluid norepinephrine and free γ-aminobutyric acid in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive degenerative neurological disease of unknown etiology. As the first step in evaluating systematically neurotransmitter metabolism in ALS, we measured norepinephrine (NE) in plasma and cerebrospinal fluid (CSF) by radioimmunoassay and γ-aminobutyric acid (GABA) in CSF by radioreceptor assay of 34 patients with ALS, 31 patients with myopathies but no central nervous system disease and 167 patients with various neurological disorders. CSF GABA was significantly decreased in ALS patients compared to myophathy ( p<0.05) and neurological ( p<0.01) patients. However CSF NE was significantly increased ( p<0.01) with respect to either comparison group. This dichotomy in neurotransmitter concentrations could result from a single neurotoxin leading to neuronal degeneration and a decrease in glutamic acid decarboxylase. The resultant decrease in GABA which is inhibitory on noradrenergic neurons could lead to the observed elevation in CSF NE due to activation of tyrosine hydroxylase.

Effect of sodium valproate on parkinsonism and L-DOPA induced dyskinesia

To investigate the role of GABA-ergic systems in parkinsonism, sodium valproate, an inhibitor of GABA catabolism, was administered to eight parkinsonian patients in a double blind, placebo controlled trial. Maximum daily doses of valproate ranged from 27 to 62 mg/kg. Parkinsonism scores were not significantly altered by valproate treatment although bradykinesia sub-scores tended to increase. L-DOPA induced dyskinesia were increased in four of the five patients with this problem and required a reduction of L-DOPA in three. Plasma L-DOPA concentrations were not influenced by valproate treatment suggesting that the enhancement of dyskinesias was not a result of alteration of peripheral L-DOPA metabolism. In six patients cerebrospinal fluid (CSF) GABA was measured by a radioreceptor assay during the placebo and the high dose valproate phases of the study. Valproate had no consistent effect on the concentration of GABA in the CSF. These results suggest that sodium valproate is of no clinical benefit in the treatment of parkinsonism or L-DOPA induced dyskinesia. Although proof that valproate augmented GABA-ergic neurotransmission is lacking, the increase of bradykinesia and L-DOPA induced dyskinesia is consonant with recent animal studies in which GABA-mimetics decreased locomotion but facilitated stereotypy induced by dopaminergic agents.

Cerebrospinal fluid GABA levels in involuntary movement disorders

GABA was measured in Cerebrospinal fluid (CSF) from patients with involuntary movement disorders to evaluate the selectivity and specificity of CSF GABA levels in diseases of the basal ganglia and cerebellum. GABA was measured by ion-exchange/fluorometric method from the first 12 ml of CSF. The results showed the mean ( ± SD) CSF GABA levels to be 233 ± 78 pmol/ml in normal controls, 141 ± 60 pmol/ ml in Hungtinton's disease, 130 ± 48 pmol/ ml in Parkinson's disease, 125 ± 89 pmol/ ml in Cerebellar degeneration and 125 ± 43 pmol/ ml in Essential tremor. Statistical comparison using the Student's t-test showed that CSF GABA level was significantly reduced in patients with Huntington's disease, Parkinson's disease, Cerebellar degeneration and Essential tremor when compared to normal controls. No statistically significant differences were found between Huntington's disease and other three diseases, showing that low CSF GABA levels are not specific for any one of these diseases. No clear correlation was seen between CSF GABA levels and age, duration, severity of illness, medication or symptoms in either Huntington's disease or Parkinson's disease.

GABA levels in CSF of neurological patients by high performance liquid chromatography

Recently we have developed a simple and sensitive assay for the measurement of GABA in fluids and tissues by high performance liquid chromatography [16]. The only sample preparation required is deproteinization and usually 100 μl of CSF is all that is required for a reliable determination of OABA. We have measured GABA CSF levels in patients with various neurological disorders as well as in a few control specimens. The control values, around 300 nM, agree with published results. Patients with Parkinson's disease or Huntington's chorea had CSF GABA levels ranging from 26–150 nM with occasional high values and are in general agreement with those reported by Enna et al. [7]. Cerebrospinal fluid GABA levels in patients with myoclonus, stroke, dystonia and other miscellaneous neurological disorders ranged from 50–600 nM, without any recognizable pattern. From the results obtained thus far, low levels of CSF GABA are not necessarily limited to patients with Huntington's chorea or Parkinson's disease.

Cerebrospinal fluid GABA variations with seizure type and cerebellar stimulation in man

GABA has been implicated in the neurochemistry of epilepsy. The mean lumbar CSF GABA concentration determined by ion-exchange/fluorometric assay among 21 medicated patients with intractable seizures was significantly lower ( p<0.001) than that of 20 age- and sex-matched unmedicated normal volunteers. Patients with grand mal and psychomotor seizures had significantly lower ( p<0.05) CSF GABA concentrations than those with focal sensory/motor epilepsy. Lumbar CSF GABA levels did not significantly correlate with serum concentrations of phenytoin, phenobarbital or primidone. Lumbar CSF GABA levels in four seizure patients were significantly lower ( p<0.02) during a combination of unilateral, alternating and bilateral, continuous cerebellar stimulation than those determined after a 7-day period without stimulation. Thus, GABA-mediated neuronal transmission appears depressed in medicated epileptic patients and further reductions evoked by cerebellar surface stimulation may compromise seizure control.

Factors influencing concentrations of GABA in cerebrospinal fluid

GAD, the GABA biosynthetic enzyme, and CSD, the enzyme which converts cysteic acid to taurine, a putative inhibitory transmitter, and cysteine sulfinate to hypotaurine, the proposed precursor of taurine, were partially copurified from rat brain. Polyvalent antisera against this preparation were raised in sheep. GAD/CSD was localized on two-dimensional electrophoresis and line immunoelectrophoresis (LIE) using the radioactive suicide substrate 2-3H-γ-Acetylenic GABA. LIE with less purified GAD/CSD and a polyvalent antiserum yielded three precipitin lines. An antiserum (1440) to the radioactively labelled precipitin line precipitated both GAD and CSD activity. On crossed immunoelectrophoresis with an intermediate gel containing antiserum 1440, the mobility of one antigen in brain homogenate supernatant was altered. Immunocytochemistry using antiserum 1440 and the indirect “PAP” method of Sternberger yielded apparently specific staining in the cerebellum and olfactory bulb.